Structural and functional features of the taste system change dramatically during development. While much has been learned by studying normal developmental processes, complementary experiments that use experimental manipulations during critical phases of development have been of great value in learning how the taste system is organized. The specific aims of this proposal use coordinated neurophysiological, morphological and immunohistochemical studies to extend our earlier findings on the development of the gustatory system from receptor to central nervous system organization. Neurophysiological studies focus on the development of sodium taste transduction pathways and on the susceptibilities of different taste receptor cell populations and associated nerves to early dietary sodium restriction. Morphological studies examine potential mechanisms responsible for the development of neuron/target matching in taste buds and examine the interrelationship between gustatory afferent projections into the first central synaptic relay. Immunohistochemical experiments explore receptor cell differences in subunit complementation of channels used in sodium taste transduction and the role that early diet has on formation of the channel. The overall focus of this proposal, therefore, is on how the gustatory system is assembled after the initial functional and structural components are present. Proposed studies will provide new information about: 1) the nature of age- and diet-related neurophysiological changes, the site of response alterations, and biophysical changes in the transducing elements in taste receptor cells, 2) the manner by which taste bud size matches numbers of innervating neurons with age, and 3) the mechanisms underlying differential susceptibilities of lingual and palatal taste receptors and associated neurons to early dietary manipulations. Findings from these studies will provide further information about the development and plasticity of the peripheral and central gustatory system. They will also be useful in determining the role that diet has on organizing the developing sense of taste.